The present invention is directed to a water sprinkler commonly used for watering lawns, such as that disclosed in U.S. Pat. No. 1,997,901--Englehart. The conventional water sprinkler has a main nozzle through which the stream of water exits, which nozzle is connected to a mounting arm that is rotatably mounted on a stem via a pivot post, so that the nozzle may be rotated a full 360 degrees to water a lawn. An oscillatory reaction lever arm is also used upon which the stream of water impinges as it exits from the nozzle, which reaction lever arm causes the slow incremental rotation of the mounting arm about the stationary stem via the energy stored in a spiral spring encircling the main pivot post, the stored energy along with the energy of the vacuum created during the return stroke of the oscillating lever arm with respect to the flowing water stream developing a torque great enough to overcome the friction between the mounting pivot post and stationary stem, whereby relative rotational movement between the pivot post and stem ensues, to bring about the rotational movement of the stem. It is also known in the prior art to provide a water-stream height-deflector to vary the range of the water-stream exiting from the nozzle so that different radial distances from the sprinkler may be watered during one complete cycle of operation. One such system is disclosed in U.S. Pat. No. 3,960,327--Olson. However these prior-art devices are difficult to reset to suit changing watering patterns, are relatively difficult to initially set up, cannot provide for a multitude of distance-changes during one complete cycle, and cannot provide the exactness often required for stream-distance settings, but must rely upon a repeated trial-and-error approach.